Fuses and fuseholders

ABSTRACT

A fuse device comprising a fuse and a fuseholder, in which a fuse element of the fuse comprises a fuse wire and goodconductive layer coated on the fuse wire except a melting center portion thereof. The fuse is provided with a spring indicator and a spring strip which are seated in parallel with each other. The fuse element is connected to respective tops of the spring indicator and the spring strip while the spring indicator is pulled to the spring strip. The fuseholder is provided with a hollow which receives the lower part of the fuse, and two fork terminals seated in the hollow to be coupled with the spring indicator and the spring strip. The fuseholder may be provided at least one alarm terminal in addition to the two fork terminals.

United States Patent Kitagawa et al.

[541 FUSES AND FUSEHOLDERS [72] Inventors: Tadashi Kitagawa; Shoichiro Yaguchi; Katsuyuki Yamanobe; Masao Kawamata, all of Tokyo, Japan [73] Assignee: Daito Tsushinki Kabushiki Knisha,

Tokyo-to, Japan [22] Filed: June 4,1971 [21] Appl. No.: 150,101

[30] Foreign Application Priority Data [51] Int. Cl....H0lh 85/56, HOlh 85/08, HOlh 85/30 [58] Field of Search ..337/158, 159, 186,190, 194, 337/198, 206, 241, 244, 261, 265, 267, 282,

[56] References Cited UNITED STATES PATENTS 3,236,952 11/1966 l lussar...... 3314296 3 (4 1 Oct. 3, 1972 Fister ..337/261 Griinwald ..337/296 Primary Examiner-Bernard A. Gilheany Assistant ExaminerDewitt M. Morgan Attorney-Robert E. Burns and Emmanuel J. Lobato [57] ABSTRACT A fuse device comprising a fuse and a fuseholder, in which a fuse element of the fuse comprises a fuse wire and good-conductive layer coated on the fuse wire except a melting center portion thereof. The fuse is provided with a spring indicator and a spring strip which are seated in parallel with each other. The fuse element is connected to respective tops of the spring indicator and the spring strip while the spring indicator is pulled to the spring strip. The fuseholder is provided with a hollow which receives the lower part of the fuse, and two fork terminals seated in the hollow to be coupled with the spring indicator and the spring strip. The fuseholder may be provided at least one alarm terminal in addition to the two fork terminals.

7 Claims, 31 Drawing Figures P'A'TENTEflnma I972 sum 2 OF 4 FUSES AND FUSEI-IOLDERS This invention relates to fuses and fuseholders used as a protective device containing a short length of special wire, that melts when the current through it exceeds the rated value for a definite period of time to isolate a fault.

Many kinds of fuses and fuseholders are used in electronic devices for electrical protection. In accordance with recent increase of the use of semiconductor elements in electronic circuitry, quick acting fuses of small current-capacity and small dimension are generally required. Moreover, since the source voltage is relatively low in electronic devices using semiconductor elements, a small resistance of each fuse is required to reduce a voltage drop across the fuse as far as possible. However, since it was very difficult to miniaturize conventional fuse elements in accordance with conventional techniques, useful fuses of small dimension have not yet been proposed. Moreover, the above difficulty increases for fuses having an alarm which is activated in response to the blowing of each fuse since the alarm is usually activated by a spring indicator which is held by means of tension of the fuse element.

An object of this invention is to provide fuses and fuseholders of small dimension capable of readily satisfying requirements for quick acting fuses.

Another object of this invention is to provide alarm activating fuses and fuseholders of small dimension.

Another object of this invention is to provide fuses and fuseholders of small dimension easily constructed so as to be suitable for different alarm circuits under usage of the same fuse.

The principal construction and other objects of this invention will be understood from the following detailed discussion in conjunction with the accompanying drawings, in which the same or equivalent parts are designated by the same reference numerals, characters and symbols, and in which:

FIGS. 1A, 1B and 1C are respectively a front view, a right side view, and a lower plane view illustrating an embodiment of a fuse of this invention;

FIG. 1D is a sectional view along a plane Id shown in Fig. 1B;

FIGS. 2A, 2B, 2C and 2D are respectively a front view, an upper plane view, a lower plane view, and a right side view illustrating an embodiment of a fuseholder of this invention;

FIG. 2B is a longitudinal section along a plane Ile shown in Fig. 28;

FIG. 2F is a cross section along a plane Ilf shown in Fig. 2A;

FIG. 2G is an elevation illustrating an example of a fork terminal used in a fuseholder of this invention;

FIGS. 3A, 3B, 3C and 3D are respectively a front view, an upper plane view, a lower plane view, and a right side view illustrating another embodiment of a fuseholder of this invention;

FIG. 3E is a longitudinal section along a plane lIIe shown in Fig. 3B;

FIG. 4 is a front view including a section illustrating a combined state of a fuse and a fuseholder of this invention;

FIGS. 5A, 5B, 5C and SD are respectively a front view, an upper plane view, a lower plane view and a right side view illustrating another embodiment of a fuseholder of this invention;

FIG. SE is a longitudinal section along a plane Ve shown in Fig. 58;

FIGS. 6A, and 6B are respectively a plane view and a side view illustrating an example of a fuse element of this invention;

FIGS. 7A and 7B are respectively a plane view and a side view illustrating another example of a fuse element of this invention;

FIGS. 8 and 9 show time-current charts explanatory of characteristics of fuse elements of this invention;

FIGS. 10A and 10B are respectively a plane view and a side view illustrating fuseholder sockets which are employed for supporting fuseholders of this invention; and

FIG. 10C is an elevation including a section illustrating a combined state of a fuseholder and a fuseholder socket of this invention.

With reference to Figs. 1A to ID, a fuse of this invention will first be described. A fuse of this invention comprises a fuse case 1, a fuse cover 2 and a fuse element 8. The fuse case 1 is of heat resisting plastic material and has two pairs of parallel grooves 30a, 30b and 31a, 31b which are respectively opposed to each other at the front and the back of the fuse case 1 and respectively connected to each other through rectangular openings 7. A spring terminal 3 associated with a spring indicator 5 so as to form a T-character is seated in grooves 31a and 31b, so that two ends of the spring terminal 3 are bent in the rectangular opening 7. A spring strip 6 is seated in the grooves 30a and 30b so as to form a terminal 4, so that an end of the spring strip 6 is bent in the rectangular groove 7'. Two ends of the fuse element 8 are respectively connected to upper ends of the spring indicator 5 and the spring strip 6 while the top of the spring indicator is pulled towards the top of the spring strip 6. The fuse case 1 has further two openings l0al and 10b1. The fuse cover 2 is of a heat-resisting plastic material and has two projections l0a2 and 10b2, which are respectively coupled to the openings Mal and l0b1 and fixed to each other by heat-clinching. The fuse cover 2 has further side walls 32 and 33 and an upper wall 34. As a result of the above construction, an upper opening 9a and a side opening 9b are provided in combination of the fuse case 1 and the fuse cover 2. The top of the spring indicator 5 is colored in a desired color, such as white. Accordingly, if the fuse element 8 is blown, the spring indicator 5 is released as shown by dotted lines 5a so that the colored top of the spring indicator 5 can be detected from the top opening 9a. Moreover, gas generated in response to blowing of the fuse element 8 is exhausted from the side opening 9b to avoid an are between the respective tops of the spring indicator 5 and the spring strip 6. The upper wall 34 has a triangular projection 35 to raise the efficiency of exhausing the generated gas.

The abovementioned fuse is used in coupling with a fuseholder of this invention, which is formed into a type A without alarm terminals, and a type B with alarm terminals. The alarm terminals may be provided in connection with or in disconnection with the terminals 3 and 4 of the fuse. In other words, the electric source for the alarm circuit may be provided commonly with or independently upon an electric source of a fuse-protected electronic circuit. If the alarm terminals are provided in disconnection with the terminals 3 and 4, the

alarm circuit may be designed in a make-contact type, a breaktcontact type, or a transfer-contact type.

With reference to FIGS. 2A to 2G, an example of the fuse holder of this invention is of a heat-resisting plastic material and formed into a case, which comprises a rectangular hollow 11a and a plastic wall 11 surrounding the rectangular hollow 11a except the upper side thereof. Two pairs of parallel grooves 12a1, 12121 and l2a2, l2b2 are provided at the inside surface of the plastic wall 11 so as to oppose to each other. A fork terminal 12 shown in FIG. 26 is downwardly inserted in each pair of the parallel grooves 12a, 12bl and l2a2,

12122 and clinched to the bottom of the plastic wall 11 by means of a click 13. A rectangular opening 11b provided at the bottom of the plastic wall 11 is employed to seat a terminal or terminals of an alarm circuit as mentioned below.

With reference to FIGS. 3A to 3E, another example of a fuseholder of this invention further comprises an alarm terminal 14 having a bent top 14a, and a plastic packing block 15 used for fixing the alarm terminal 14 in the rectangular opening 11b in the bottom of the plastic wall 11. The plastic packing block 15 and the alarm terminal 14 are fined in the rectangular opening by the use of plastic wedges 15a and 15b.

The fuse shown in FIGS. 1A to 1D is coupled to the fuseholder shown in FIGS. 3A to 3E as shown in Fig. 4, in which the terminals 3 and 4 are coupled to the fork terminals 12. In Fig. 4, the cover 2 of the fuse are eliminated except the side walls 32 and 33 and the upper wall 35 for ready understanding of the coupled state. If the fuse element 8 is blown, the spring indicator 5 is released to the left side so that the top 14a of the alarm terminal 14 contacts with the released spring indicator 5. Accordingly, an alarm circuit is formed between the terminals 12 and 14.

With reference to FIGS. 5A to SE, another example of the fuseholder of this invention provides with, in addition to means shown in FIGS. 2A to 2G, alarm terminals l4 and 16, a spring strip 17 contacted with the terminal 16, and a plastic cap 18. The top of the spring strip 17 and the top 148 of the terminal 14 provide a make contact of an alarm circuit, which is activated by another alarm source in response to the blowing of the fuse element 8. The plastic cap 18 is provided for avoiding danger of an arc, which may be formed between the spring indicator 5 and the top of the alarm terminal 14 or 16 in releasing the spring indicator 5.

With reference to FIGS. 6A and 63, an example of the fuse element 8 comprises a small fuse wire 8a having a diameter d, and good-conductive layers 8c (e.g.; silver) coated on the fuse wire 8a except a melting center portion of a length L in accordance with electrical plating or vacuum evaporation. The conductive layers 80 are employed for soldered-joint or weldingjoint to the respective tops of the spring strip 6 and the spring indicator 5 and for thermoradiation. The current/time charts of this fuse element are shown in Fig. 8, in which the characteristic curve varies as shown by curves a, b and c in accordance with decrease of the length L of the melting center portion. Rated current I I and l correspond respectively to the curves A, B and C. As understood from Fig. 8, the rated current of the fuse element of this invention decreases in accordance with increase of the length L of the melting center portion while the diameter d of the fuse wire 8a can be maintained at a constant value. The fuse wire 8d may be replaced by a fuse strip 8b having a width w.

A characteristic of a limited current fuse is shown by a curve A in Fig. 9, while a characteristic of a quick acting fuse is shown by a curve B in Fig. 9. The limited current fuse is not blown by a current equal to l 10 percent of the rated current I. under the standard characteristic, but the blowing time T, of the limited current fuse for a current equal to twice the rated current 1 must be less than 2 minutes. On the other hand, the standard blowing time T of the quick acting fuse must be less than 0.5 seconds for a current equalto twice the rated current 1 while the quick acting fuse is not blown by a current equal to 110 percent of the rated current 1,. As understood from Fig. 8, respective characteristics shown by the curves a, b and c satisfy the above requirements, and blowing times T, and T satisfy the time limit (T for the blowing time of the quick acting fuse.

An example of the fuse element has a diameter d of one hundredth of several millimeters to several tens millimeters, and a diameter D of the thermo-radiation part (ic) equal to several times the diameter d of the melting part. Accordingly, the diameter D is substantially equal to l milimeter. The length L of the melting part is determined at L suitable value in a region of several millimeters to several tenth millimeters in consideration of a rated current and a rated resistance.

The above mentioned fuse element of this invention has the following merits over conventional fuse elements:

(a) Since the length L of the melting center part can be precisely determined by the use of optical techniques, such as photo-etching, deviation of the resistance and the blowing time is very small.

(b) Since the thermo-radiation parts of the fuse element are coated by a good conductor, the resistance of the fuse element can be maintained at a constant value in disregard of connection techniques of the fuse element to the respective tops of the spring indicator 5 and the spring strip 6.

(c) Quick acting fuses can be readily obtained in accordance with this invention.

(d) Since the resistance of the fuse element is not at all effected by a tension applied thereto, reliable alarm fuses can be readily produced in accordance with this invention.

(e) Vibration characteristic of fuses is effectively improved in accordance with this invention.

The fuseholders of this invention are supported by suitable supporting means. An example of the supporting means comprises, as shown in FIGS. 10A and 108, a spring metal plate 20 (e.g., a stainless steel plate) which has a plurality of punched-out rectangular openings 22 arranged side by side, so that the supporting means is formed into a ladder shape. Each of the rectangular openings 22 has triangular projections 21 at longitudinal edges thereof. The fuseholder is inserted in the opening 22. The plate 20 may be used as shown in FIG. 10C, in which the fuseholder is inserted in an opening of a supporting plate 23 while the plate 20 is clinchedunder the supporting plate 23 by the use of the projections 21.

What we claim is:

1. A fuse device, comprising a fuse and a fuseholder;

the fuse comprising a fuse case, a fuse cover and a fuse element; the fuse case being a plastic plate and having two pairs of parallel grooves which are respectively opposed to each other at the front and the back of plastic plate, a spring terminal associated with a spring indicator so as to form a T-character being seated in one pair of said opposed grooves, a spring strip being seated in another pairs of said opposed grooves; the fuse element being connected to respective tops of the spring indicator and the spring strip while the top of the spring indicator is pulled towards the top of the strip, the fuse element comprising a fuse wire coated with good-conductive layers except a melting portion; the fuse cover being associated with the fuse case so as to form an upper opening employed for detecting the top of the spring indicator when released and a side opening employed for exhausting a gas generated when the fuse element is blown;

the fuseholder being a plastic case having a rectangular hollow and a plastic wall surrounding the rectangular hollow except the upper side thereof, two pairs of parallel grooves being provided at the inside surface of the plastic wall so as to oppose to each other, two fork terminal being respectively seated in said two pairs of parallel grooves;

a lower part of the fuse being coupled to the rectangular hollow of the fuseholder so that said spring terminal and said spring strip are respectively coupled to said fork terminals.

2. A fuse device according to claim 1, inwhich the good-conductive layer is electrically plated on the fuse wire.

3. A fuse device according to claim 1, in which the good-conductive layer is deposited on the fuse wire by vacuum evaporation.

4. A fuse device according to claim 1, in which the fuseholder further comprises an alarm terminal provided in parallel with the two fork terminals so as to contact with the spring indicator when released.

5. A fuse device according to claim 1, in which the fuse holder further comprises at least two alarm terminals provided in parallel with the two form terminals so as to be activated when the spring indicator of released.

6. A fuse device according to claim 5, in which further comprises an insulative cap provided at the top of said at least two alarm terminals.

7. A fuse device according to claim 1, in which further comprises a supporting plate having a rectangular opening coupled with the fuseholder, triangular projections being provided at longitudinal edges of the rectangular opening for clinching f the fuseholder. 

1. A fuse device, comprising a fuse and a fuseholder; the fuse comprising a fuse case, a fuse cover and a fuse element; the fuse case being a plastic plate and having two pairs of parallel grooves which are respectively opposed to each other at the front and the back of plastic plate, a spring terminal associated with a spring indicator so as to form a ''''T''''-character being seated in one pair of said opposed grooves, a spring strip being seated in another pairs of said opposed grooves; the fuse element being connected to respective tops of the spring indicator and the spring strip while the top of the spring indicator is pulled towards the top of the strip, the fuse element comprising a fuse wire coated with goodconductive layers except a melting portion; the fuse cover being associated with the fuse case so as to form an upper opening employed for detecting the top of the spring indicator when released and a side opening employed for exhausting a gas generated when the fuse element is blown; the fuseholder being a plastic case having a rectangular hollow and a plastic wall surrounding the rectangular hollow except the upper side thereof, two pairs of parallel grooves being provided at the inside surface of the plastic wall so as to oppose to each other, two fork terminal being respectively seated in said two pairs of parallel grooves; a lower part of the fuse being coupled to the rectangular hollow of the fuseholder so that said spring terminal and said spring strip are respectively coupled to said fork terminals.
 2. A fuse device according to claim 1, in which the good-conductive layer is electrically plated on the fuse wire.
 3. A fuse device according to claim 1, in which the good-conductive layer is deposited on the fuse wire by vacuum evaporation.
 4. A fuse device according to claim 1, in which the fuseholder further comprises an alarm terminal provided in parallel with the two fork terminals so as to contact with the spring indicator when released.
 5. A fuse device according to claim 1, in which the fuse holder further comprises at least two alarm terminals provided in parallel with the two form terminals so as to be activated when the spring indicator of released.
 6. A fuse device according to claim 5, in which further comprises an insulative cap provided at the top of said at least two alarm terminals.
 7. A fuse device according to claim 1, in which further comprises a supporting plate having a rectangular opening coupled with the fuseholder, triangular projections being provided at longitudinal edges of the rectangular opening for clinching f the fuseholder. 